Calibration of foreign object detection in wireless power systems with authentication

ABSTRACT

Apparatus and methods are described for performing wireless power transfer and foreign object detection with authentication at different power levels. The impact of time required for an authentication process to execute between transitions to different power levels is reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Division of U.S. application Ser. No. 16/987,192,filed Aug. 6, 2020, and entitled “CALIBRATION OF FOREIGN OBJECTDETECTION IN WIRELESS POWER SYSTEMS WITH AUTHENTICATION,” which claimspriority to U.S. Provisional Application Ser. No. 62/887,051, filed Aug.15, 2019 and entitled “CALIBRATION OF FOREIGN OBJECT DETECTION INWIRELESS POWER SYSTEMS WITH AUTHENTICATION,” each of which is herebyincorporated by reference in its entirety.

BACKGROUND 1. Technical Field

The techniques described herein relate to wireless power delivery,detection of foreign objects in a wireless power transfer region, and totransitioning between different modes of operation.

2. Discussion of the Related Art

Wireless Power Transfer Systems (WPTS) are gaining increasing popularityas convenient way to deliver power without wires or connectors. WPTScurrently under development in the industry can be separated in twomajor classes: magnetic induction (MI) systems and magnetic resonance(MR) systems. Both types of systems include a wireless power transmitterand a wireless power receiver. Inductive WPTS typically operate in anallocated frequency range of several hundred kilohertz using frequencyvariation as a power flow control mechanism. MR WPTS typically operateon a single resonant frequency using input voltage regulation toregulate output power. In some applications, MR WPTS operate at afrequency of 6.78 MHz. Such systems can be used to power or chargeconsumer-electronic devices such as smartphones, calculators, cameras,and tablet computers, and may be used for other applications.

SUMMARY

Some wireless power transfer systems are capable of providing powerwirelessly at high power levels (e.g., above 5 watts). In some cases,power levels of 15 watts or more may be transmitted wirelessly. Whenoperating at high power levels, it is desirable to avoid deliveringlarge amounts of power to foreign objects that could be located in awireless power transfer region. In some cases, it is also desirable toassure that a wireless power receiver and/or wireless power transmitterare certified or qualified for transferring high power levels. As aresult, authentication and foreign object detection steps may beexecuted prior to transferring high power levels. In someimplementations, authentication and/or foreign object detection stepsmay be executed when a wireless power transmitter and wireless powerreceiver change from a first mode of operation (which may be anon-privileged mode that is available to all such devices) to a secondmode of operation (which may be a privileged mode that is restricted tocertain authorized devices). Embodiments described herein relate tomethods for wireless power transfer at high levels of power when foreignobjects might be present and also to transitions between non-privilegedand privileged modes of operation by wireless power transmitters andwireless power receivers.

Some embodiments relate to control logic for a wireless power receiverthat adapt the wireless power receiver to: establish wireless powerreception during a wireless power transfer session from a wireless powertransmitter at a first power level; execute an authentication processwith the wireless power transmitter; if the authentication processcompletes successfully, send session attribute information to memory;receive session attribute information from the memory after interruptionof wireless power reception at the first power level at the wirelesspower receiver; and establish wireless power reception from the wirelesspower transmitter at a second power level that is higher than the firstpower level.

Some embodiments relate to methods of receiving power wirelessly by awireless power receiver during a wireless power transfer session. Suchmethods may comprise acts of: establishing wireless power reception froma wireless power transmitter in a first mode of operation; executing anauthentication process with the wireless power transmitter; sendingsession attribute information to memory, wherein the session attributeinformation includes at least some information relating to theauthentication process; receiving session attribute information afterinterruption of wireless power reception in the first mode of operationat the wireless power receiver; and establishing wireless powerreception from the wireless power transmitter in a second mode ofoperation after receiving the session attribute information.

Some embodiments relate to controllers for a wireless power transmitterthat are adapted with code to: establish wireless power transmission toa wireless power receiver at a first power level; execute anauthentication process with the wireless power receiver; send sessionattribute information relating to the authentication process to memory;perform a foreign object detection process during a time when wirelesspower reception at the first power level at the wireless power receiveris interrupted; and transmit at least some of the session attributeinformation retrieved from the memory to the wireless power receiverprior to transmitting power wirelessly at a second power level that ishigher than the first power level.

Some embodiments relate to methods of transmitting power wirelessly by awireless power transmitter. Such methods may comprise acts of:establishing wireless power transmission to a wireless power receiver ina first mode of operation; executing an authentication process with thewireless power receiver; performing a foreign object detection processduring a time when wireless power reception at the wireless powerreceiver in the first mode of operation is interrupted after executingthe authentication process; re-establishing wireless power transmissionto the wireless power receiver in the first mode of operation; andestablishing wireless power transmission to the wireless power receiverin a second mode of operation after performing the foreign objectdetection process.

The foregoing summary is provided by way of illustration and is notintended to be limiting.

BRIEF DESCRIPTION OF DRAWINGS

In the drawings, each identical or nearly identical component that isillustrated in various figures is represented by a like referencecharacter. For purposes of clarity, not every component may be labeledin every drawing. The drawings are not necessarily drawn to scale, withemphasis instead being placed on illustrating various aspects of thetechniques and devices described herein.

FIG. 1 is a block-diagram depiction of a wireless power system includinga wireless power transmitter and a wireless power receiver, according tosome embodiments.

FIG. 2A depicts an example of acts associated with wireless powertransfer methods that can be performed by a wireless power transmitter,according to some embodiments.

FIG. 2B depicts an example of acts associated with wireless powertransfer methods that can be performed by a wireless power transmitter,according to some embodiments.

FIG. 3 depicts an example of acts associated with wireless powertransfer methods that can be performed by a wireless power receiver,according to some embodiments.

DETAILED DESCRIPTION

Wireless power systems can provide a convenient way to provide powerfrom a first device (e.g., wireless power transmitter) which may act asa charging device to a second device needing power (e.g., a wirelesspower receiver) without the need of plugging and unplugging one or morepower chords. In many implementations, the wirelessly provided power canbe used to power and/or charge an electronic device. Some wireless powersystems can operate in two or more modes of wireless power transfer thatmay correspond to different levels of wireless power transfer.

For example, a wireless power system 100 (such as the one depicted inFIG. 1) having a transmitter 1 and receiver 11 can operate in alow-power mode. An amount of power transferred in a low-power mode canbe 5 watts or less, according to some embodiments. In some cases, such amode may be referred to as a “basic power performance” mode, thoughother designations may be used. Power levels delivered to foreignobjects and wireless power receivers at low-power modes of operation maynot cause high heating conditions or exceed standard operatingconditions for the receivers. Heating may be caused, for example, by aforeign object 20 (such as a paper clip, coin, etc.) that isinadvertently located in a wireless power transfer region between thetwo devices. In the wireless power transfer region, electromagneticfields can impinge on the foreign object 20 and potentially generatecurrents in the foreign object, which may be dissipated as heat.

Foreign objects 20 can also adversely affect efficiency of wirelesspower transfer. Wireless power transfer can be degraded due to thepresence of a conductive foreign object 20 in the field produced by thewireless power transmitter. A conductive and/or metallic object mayabsorb power due to the inducement of currents in the object. If a metalobject is present, efficiency of power transfer may be reducedsubstantially (e.g., from 90% to 40%). Therefore, it can be beneficialto detect foreign objects and calibrate the wireless power system 100 toaccount for the foreign object(s) prior to providing power wirelessly atany power level for an extended period of time.

A wireless power system 100 can operate in one or more high-power modes.For example, a high-power mode may be a mode in which wireless powertransfer at power levels over 5 watts can occur. In some cases, ahigh-power mode may transfer power levels from 5 watts up to 15 watts,or even higher. Such a mode or modes may be referred to as “extendedpower performance,” though other designations may be used. As may beappreciated, undesirable power loss and heating conditions can increasewith increased power-transfer levels. Accordingly, it can be beneficialto further perform foreign-object detection (FOD) and calibration toaccount for foreign objects before entering high-power modes as well asperforming FOD intermittently during operation in high-power modes.

Some wireless power receivers 11 may not be configured to handle highlevels of power transfer from a wireless power transmitter 1. Forexample, they may have internal electronic components that are not ratedfor the higher power levels that a transmitter 1 can provide. For suchreceivers, an authentication procedure may be implemented beforeattempting to enter high-power modes of operation. An authenticationprocedure may determine, for example, that a receiver 11 complies with astandard (such as the Qi standard) to which the transmitter 1 alsocomplies and is rated for one or more high-power modes of operation.

The inventor has recognized and appreciated that an authenticationprocedure between a wireless power transmitter 1 and wireless powerreceiver 11 can take an appreciable amount of time (e.g., more than 5seconds, more than 10 seconds, or more than 20 seconds in some cases).During such time intervals, conditions relating to a foreign object 20can change. For example, the foreign object if present may be moved, ora foreign object 20 may be inadvertently placed in the wireless powertransfer region during the time interval. Therefore, FOD andcalibrations performed in a low-power mode of operation may no longer bevalid when entering a high-power mode of operation after performing alengthy authentication procedure. The change in foreign objectconditions may result in an undesirable operating condition ifhigh-power operation is allowed.

Further details of a wireless power transfer system 100 and foreignobject detection are now described briefly before describing methods toavoid undesirable operating conditions when performing authenticationprocedures and transitioning to high-power operating modes.

FIG. 1 shows a block diagram of a wireless power system 100 including awireless power transmitter 1 and a wireless power receiver 11. Thewireless power transmitter 1 has a drive circuit 7 that can include aninverter 3 and matching network 6. The inverter 3 can drive a transmitcoil 10 and be impedance matched to the transmit coil through a matchingnetwork 6.

According to some embodiments, the wireless power transmitter 1 canfurther include a regulated voltage source 2 (e.g., a voltage regulator)that provides a regulated DC voltage to the inverter 3. The regulatedvoltage source 2 produces a regulated DC output voltage in response tocontrol stimulus from the controller 5. In some embodiments, the drivecircuit 7 may be a class D or E amplifier that converts the DC voltageat the input of inverter 3 into an AC output voltage to drive thetransmit coil 10. Producing an AC output voltage enables wireless powertransmission through electromagnetic induction.

The controller 5 may also control a signal generator 9 to drive theinverter 3 with signals of a selected wireless power transmissionfrequency. As an example, the inverter 3 may be switched at a frequencybetween 100 and 205 kHz to transmit power to a wireless power receiverdesigned to receive wireless power according to the Qi specification forlow power Qi receivers and 80-300 kHz for medium power Qi receivers. Theinverter 3 may be switched at a higher frequency, such as a frequency ofgreater than 1 MHz, within an ISM band, e.g., 6.765 MHz to 6.795 MHz, totransmit power to a receiver designed to receive wireless power using MRtechnology. However, these frequencies are provided merely by way ofexample, as wireless power may be transmitted at a variety of suitablefrequencies, in accordance with any suitable specification. Controller 5may be an analog circuit or a digital circuit. Controller 5 may beprogrammable, and may command signal generator 9 to produce signals at adesired transmission frequency based on stored program instructions, sothat inverter 3 switches at the desired transmission frequency.

Matching network 6 may comprise one or more impedance-matching networksand facilitate wireless power delivery by presenting a suitableimpedance to the inverter 3. The matching network(s) may have one ormore capacitive or inductive elements or any suitable combination ofcapacitive and inductive elements. Since the transmit coil 10 may havean inductive impedance, in some embodiments the matching network 6 mayinclude one or more capacitive elements, which, when combined with theimpedance(s) of the transmit coil 10, presents an impedance to theoutput of inverter 3 suitable for driving the transmit coil 10. Forexample, the matching network may rotate an input impedance of thetransmit coil 10 to approximately an output impedance of the inverter 3,so as to reduce power reflection that would otherwise occur from thetransmit coil 10. In some embodiments, during wireless power transfer,the resonant frequency of the matching network 6 and transmit coil 10can be adjusted (e.g., by variable capacitors and/or switching in andout capacitors) and can be set equal to or approximately equal to theswitching frequency of the inverter 3.

The transmit coil 10 and receive coil 12 may be realized by any suitabletype of conductors. The conductors may be wires, including solid,single-core wire or Litz wire. In some cases, a coil can be formed frompatterned conductors, such as patterned conductors of a printed-circuitboard or an integrated circuit.

AC current that is driven in the transmit coil 10 can generate anoscillating magnetic field in accordance with Ampere's law. Theoscillating magnetic field can induce an AC current in, and voltageacross, a nearby receiver coil 12 of the wireless power receiver 11 inaccordance with Faraday's law. The AC voltage induced across thereceiver coil 12 is provided through a matching network 13 to arectifier 14 that generates an unregulated DC voltage. Rectifier 14 maybe a synchronous rectifier or may be implemented using diodes and one ormore capacitors. The unregulated DC voltage can be regulated using aDC/DC converter 15, the output of which may be filtered and provided toa load as output voltage V_(out). In some alternate embodiments theDC/DC converter 15 can be replaced by a linear regulator or batterycharger, or eliminated altogether.

According to some implementations, a wireless power receiver 11 mayinclude memory 17 and control logic 16. Control logic 16 can compriseapplication-specific circuitry (such as an application-specific circuitformed of logic gates and buffers, among other circuit components), oneor more field-programmable gate arrays, a microcontroller, amicroprocessor, or some combination thereof. The memory can include oneor both of volatile and non-volatile types of memory. The control logic16 can be in communication with the memory 17 and may further be incommunication with one or both of the rectifier and DC/DC converter orlinear regulator or battery charger.

In some embodiments, the wireless power transmitter 1 may havecommunication circuitry (e.g., within or connect to controller 5) forcommunicating with wireless power receiver 11. The communication can bethrough in-band communication or out-of-band communication. Similarly,wireless power receiver 11 may have communication circuitry (e.g.,within or connected to control logic 16) for communicating with awireless power transmitter 1. According to some embodiments, thewireless power receiver 11 may send information to the wireless powertransmitter 1 indicating the power demanded at the wireless powerreceiver 11, or request a change in the power level to be provided bythe wireless power transmitter 1. In response, the wireless powertransmitter 1 may increase or decrease its power output accordingly. Thewireless power transmitter 1 may control the amount of power transmittedby varying the voltage drive level applied to the transmit coil 10, thefrequency of the oscillating voltage applied to the transmit coil 10, orboth. Any suitable power control techniques may be used.

As illustrated in FIG. 1, a conductive foreign object 20 may enter awireless power transfer region in which the field produced by thetransmit coil 10 of the wireless power transmitter 1 is present. If so,the wireless power transmission efficiency can be degraded and/or powercan be dissipated and lost in the conductive foreign object 20. Examplesof conductive foreign objects 20 include, but are not limited to coins,paperclips, keys, jewelry, pens, pencils, metalized pharmaceutical ormedical objects, metal personal care products, etc.

According to some embodiments, a wireless power transmitter 1 can beconfigured to perform foreign object detection automatically, orsemi-automatically, prior to and/or during wireless power transmission.By performing foreign object detection and/or foreign objectcalibration, a wireless power transmitter 1 can determine whether or notto perform wireless power transmission to a receiver 11.

In some implementations, foreign object detection can be performed bymeasuring a quality factor Q associated with the transmit coil 10. Forexample, the wireless power transmitter 1 can excite a resonance in thetransmit coil 10 and then allow the stored energy to decay. The observedrate of decay is dependent upon the Q of the transmit coil andparameters of the circuit in which it exists, and can also be affectedby the presence of any foreign objects 20 that can interact with theelectromagnetic field produced by the transmit coil 10. Examples offoreign object detection methods are described in further detail in U.S.patent application Ser. No. 15/957,704, titled “Detecting ForeignObjects in Wireless Power Transfer Systems,” filed Apr. 19, 2018, whichapplication is incorporated herein by reference in its entirety.According to some embodiments, a method referred to as “loss balancing”can be used alternatively or additionally to determine an effect offoreign objects 20 on wireless power transfer. In loss balancing, powerlosses associated with the wireless power transmitter 1 and wirelesspower receiver 11 are known or predetermined (e.g., determined duringmanufacture of the devices). During power transfer, an amount of powerreceived by the receiver 11 can be communicated to the wireless powertransmitter. A difference between an expected amount of power received(based on power transmitted, transmitter losses, and receiver losses)and the actual power received can be attributed, at least in part, topower loss associated with one or more foreign objects.

In some implementations, if the power loss associated with foreignobject(s) exceeds a threshold value during a loss-balancing calibration,wireless power transfer will be interrupted so that the foreign object20 can be removed. Some standards, such as the Qi standard, may haveseveral threshold values that depend upon the mode of operation. Forexample, wireless power transfer may be interrupted if power lossassociated with a foreign object exceeds 350 milliwatts in a low-powermode of operation and exceeds 750 milliwatts in a high-power mode ofoperation. It will be appreciated that other threshold values may beused in the Qi standard or other standards, and the invention is not solimited to only these example values.

Acts associated with methods for wireless power transfer in differentmodes of operation, authentication, and detection of foreign objects arelisted in the flow diagrams of FIG. 2A, FIG. 2B, and FIG. 3. Actsdescribed in FIG. 2A and FIG. 2B can be performed by a wireless powertransmitter. Acts described in FIG. 3 can be performed by a wirelesspower receiver. The acts can significantly reduce the impact of alengthy authentication process on transitioning to a high-power mode ofwireless power transfer.

According to some embodiments, a method 200 of wireless power transfermay begin after a wireless power transmitter 1 is turned on and detects(act 205) a wireless power receiver (abbreviated as PRX) in a wirelesspower transfer region. The wireless power receiver 11 may be detected,in some cases, by the transmitter 1 issuing a digital or analog pingthat can induce a response from the wireless power receiver. Forexample, the wireless power receiver 11 may return identificationinformation and/or a request for wireless power transfer.

A wireless power transmitter 1 may then begin a wireless power transfersession with the receiver and execute (act 210) a foreign objectdetection process before transmitting power wirelessly to the wirelesspower receiver 11. An example of a FOD process may comprise evaluating aquality factor Q of the transmit coil 10, as described above. Thewireless power transmitter 1 and wireless power receiver 11 mayestablish (act 215) a power-transfer contract in a first mode ofoperation. The power contract in the first mode of operation may includespecifications for oscillation frequency and/or amplitude of modulation(e.g., peak-to-peak voltage) at one or both of the transmitter andreceiver. In some cases, a power metric may be included in the powercontract, such as average power detected at one or both of thetransmitter and receiver. The terms of the power contract may be used toestablish wireless power transmission to the wireless power receiver 11at a first power level associated with the first mode of operation.

Having established a power contract, a wireless power transmitter 1 mayperform (act 220) a calibration process for wireless power transfer, forwhich one or more foreign objects may or may not be present in thewireless power transfer region. The calibration process may determinepower-transfer loss associated with the foreign object and adjustwireless power transfer parameters (e.g., frequency and/or voltagelevels) to reduce such losses. According to some implementations, thepower-transfer loss may be determined by a loss-balancing process, asdescribed above.

In many wireless power transfer sessions, a wireless power receiver 11may issue a request for wireless power transfer in a second mode ofoperation that involves a higher power level than the first mode ofoperation. The request can come, in some cases, immediately after thewireless power transmitter 1 performs (act 220) a calibration process.The request can be received (act 225) by the wireless power transmitter1. In some wireless power-transfer protocols or standards, wirelesspower transfer at the higher power level may not be permitted unless anauthentication process is executed and completed successfully betweenthe wireless power transmitter 1 and wireless power receiver 11. Theauthentication process ostensibly can avoid undesirable operatingconditions that are described above (e.g., attempting to transfer a highpower level to a device that is not rated for the power level or is notcertified and registered to handle the higher power level). In responseto a request for wireless power transfer in a second mode of operation,a wireless power transmitter 1 and wireless power receiver 11 canexecute (act 230) an authentication process. In some cases, theauthentication process can involve a lengthy process of informationexchange by means of in-band or out-of-band communication between thetwo devices. In some implementations, the wireless power receiver 11initiates the authentication process. In some cases, the wireless powertransmitter 1 can initiate the authentication process.

The authentication process can involve determining the identity and/ortype of wireless power receiver 11, and determining that the receiver israted for a high-power level. In some cases, the authentication processcan involve making the identity and/or type of the wireless powertransmitter 1 known to the receiver 11 and confirming, by the receiver11, that the transmitter has been manufactured in accordance withacceptable industry specifications and established quality controlprocedures (e.g., complies with industry standards). The authenticationprocess may include retrieval of a secure key or a public key by one orboth of the transmitter 1 and receiver 11, according to someembodiments.

As explained above, an authentication process can take a significantamount of time compared to other wireless power-transfer processes thatare executed before wireless power transfer at a particular power levelcommences. As an example, the time associated with acts 205 through 225in FIG. 2A may take approximately 1.5 seconds for a wireless powerreceiver 11 and wireless power transmitter 1 operating according to theQi standard. Executing an authentication process (act 230) can takeapproximately 20 seconds or significantly more in some cases. As notedabove, the inventor has recognized and appreciated that such an intervalof time can allow for changes in foreign object conditions and possiblyresult in an undesirable operating condition. The acts of FIG. 2B cangreatly reduce the chances that such undesirable operating conditionscould arise.

According to some embodiments and referring to FIG. 2B, after anauthentication process is completed, a method 200 of wireless powertransfer may continue with determining (act 235) whether operation inthe second mode is allowed. For example, if the authentication processcould not complete successfully (which can occur if the transmitter 1 orreceiver 11 does not comply with a same wireless power-transfer standardas the receiver 11 or transmitter 1, respectively, or cannot complete akey deciphering process), then the wireless power receiver 11 andwireless power transmitter 1 can operate (act 240) in the first mode ofoperation for the remainder of the wireless power-transfer session.

On the other hand, if it is determined (act 235) that operation in thesecond mode is allowed (e.g., authentication completes successfully),then the wireless power transmitter 1 can execute several acts inpreparation for power transfer at a higher power level. In someimplementations, a wireless power transmitter 1 may receive (act 245) atleast some session attributes from a wireless power receiver 11 andstore the session attributes. The session attributes can containinformation relevant to a particular wireless power transfer session(e.g., operating information for the receiver 11 and/or transmitter 1).In some cases, session attributes can include authentication informationfrom a successfully-completed authentication process. The authenticationinformation may include information relevant to the receiver's and/ortransmitter's successful completion of the authentication process (e.g.,information needed for or resulting from the authentication process). Insome cases, the authentication information may include confirmationinformation from the receiver that authentication has been completedsuccessfully. Additionally or alternatively, session attributes maycontain other information that can be unique to the current session(e.g., any one or some combination of: receiver identification, randomlygenerated number, an encrypted key, time, date, power level, oscillationfrequency, etc.). The session attributes can be sent to a data storagelocation (e.g., volatile or non-volatile memory 4 that is a part of,and/or in communication with, the transmitter's controller 5). Later, atleast some of the session attribute information can be retrieved andused to more quickly transition from a first mode of operation to asecond mode of operation. The session attributes may also includeauthentication information from the wireless power transmitter 1. Insome cases, at least some of the session attribute information can besent back to the receiver at a later time so that the receiver can usethe session attribute information to quickly proceed with wireless powertransfer at a second power level. Session attribute information may beproduced by one or both of the transmitter 1 and receiver 11.

According to some embodiments, a method 200 may include sending (act250) a power-down command to a wireless power receiver 11 that inducesthe receiver to interrupt temporarily power transfer from its receivecoil 12 at the first power level. In some cases, the receiver maycompletely power down. In other cases, the wireless power receiver 11may disable power draw from its receive coil, and yet continue alow-power draw from an in-device power-storage element, such as a bulkcapacitor of the rectifier 14. In some implementations, charge stored inthe bulk capacitor can be used to reverse bias diodes of the rectifierto essentially block current draw from the receive coil 12 for a briefperiod of time. Such a brief period of time can allow the wireless powertransmitter 1 to execute (act 255) foreign object detection again (e.g.,evaluate the Q factor) before initiating wireless power transfer in afirst mode of operation.

According to some embodiments, instead of sending (act 250) a power-downcommand to the wireless power receiver 11, the transmitter maytemporarily interrupt wireless power transfer to the receiver 11 at thefirst power level, such that power reception at the receiver 11 at thefirst power level is temporarily interrupted. During the temporaryinterruption, the transmitter 1 can execute (act 255) foreign objectdetection. Accordingly, the receiver 11 may initiate interruption ofwireless power reception at the first power level or the transmitter 1may initiate interruption of wireless power transmission from thetransmitter 1 and reception at the receiver 11 at the first power level.

When executing (act 255) foreign object detection, the transmitter 1 mayreduce power to its transmit coil 10 (compared to a previous level forwireless power transfer during the session), so that a low level ofvoltage and power is generated at the receive coil 12. Reducing thepower to the transmit coil 10 can make it easier for the receiver 11 tointerrupt received power from its receive coil 12.

In some cases, a power-down command may not be sent to the wirelesspower receiver 11. Instead, the wireless power receiver mayautomatically power down after the authentication process and signal tothe wireless power transmitter 1 when it is powering down and/ordisabling its receive coil 12. Therefore, the act of sending (act 250) apower-down command may not be performed by a wireless power transmitter1 and not included in method 200 (as indicated by the dotted line). Insome cases, the wireless power transmitter 1 may receive a signal fromthe wireless power receiver 11 that it is powering down and/or disablingits receive coil 12.

A method 200 of performing wireless power transfer by a transmitter mayinclude executing (act 255) foreign object detection and establishing(act 260) a power contract for wireless power transfer in a first modeof operation. These two acts may be essentially the same as acts 210 and215 described above. The receiver 11 may power up and/or signal that ithas powered up or is ready for wireless power transfer after foreignobject detection (act 255) has been performed. If the wireless powertransmitter 1 has received (act 245) session attributes from thewireless power receiver 11, then the wireless power transmitter 1 maysend (act 265) session attribute information back to the wireless powerreceiver 11 that has awakened from its power-transfer interruption. Ifsession attributes were not received from the receiver, this step may beomitted from the method 200, as is indicated by the dashed outline. Thesession attribute information sent to the receiver 11 from thetransmitter 1 or received by the receiver 11 from its memory 17 caninclude information that permits the following two acts of wirelesspower transfer in the second mode of operation.

A wireless power transmitter 1 can then proceed to establishing (act270) a power contract with the wireless power receiver 11 in the secondmode of operation, which can be a high-power mode. After establishingthe power contract, the wireless power transmitter 1 can perform (act275) a calibration process during wireless power transfer, for which oneor more foreign objects 20 may be present in the wireless power transferregion, in the second mode of operation. The calibration process mayinclude acts of loss balancing. The calibration process can occur one ormore times while the wireless power transmitter 1 operates (act 280) inthe second mode of operation.

In some embodiments, the session attributes can be thought of as asession key that is created as a result of successful completion of theauthentication process (act 230). By exchanging the session attributes,the wireless power transmitter 1 and wireless power receiver 11 canquickly proceed from the second act of establishing a power contract(act 260) for the first mode of operation to operating (act 280) in thesecond mode of wireless power transfer. For example, the amount of timeafter establishing (act 260) the power contract for the first mode ofoperation to operating (act 280) in the second mode can be approximately2.5 seconds for a transmitter and receiver operating according to the Qistandard. This can be significantly shorter than and can avoid a muchlonger delay (e.g., up to 20 seconds or more) associated with theauthentication process that would otherwise occur between the two actsof establishing (act 260) a power contract in a first mode of operationand operating (act 280) in a second, higher-power, mode of operation.Because of the significantly reduced time, there can be a much smallerchance that conditions associated with one or more foreign objects 20could change between, for example, establishing power contracts for thefirst and second modes of operation. In cases where authentication doesnot complete successfully (e.g., authentication information is notvalidated by the receiver 11 or transmitter 1), then the acts ofcalibration (220, 320) may be repeated after later acts of establishing(260, 360) a power contract in the first mode of operation.

There can be corresponding acts performed by a wireless power receiver11 during a method 300 of performing wireless power transfer, asdepicted in FIG. 3. According to some embodiments, a wireless powerreceiver 11 may activate (act 305) a charging mode when placed in awireless power transfer region of a wireless power transmitter 1. Insome cases, the charging mode may be activated in response to a pingfrom the transmitter. In some implementations, the receiver 11 may pingthe transmitter 1 to indicate its presence and/or readiness forreceiving power wirelessly. A wireless power receiver 11 can participatein establishing (act 315) a power contract in a first mode of operation,in which a wireless power transmitter 1 participates. Establishing apower contract can exchange information, as described above, with thewireless power transmitter 1, and establish wireless power reception atthe receiver. A wireless power receiver 11 can further participate inperforming (act 320) calibration for power transfer during the firstmode of operation, for which one or more foreign objects may be present.

After completing the calibration process, a wireless power receiver 11can issue (act 325) a request for wireless power transfer in a secondmode of operation, and then participate in executing (act 330) anauthentication process with the wireless power transmitter 1. The method300 may or may not further include determining (act 335) whetheroperation in the second mode is allowed, based on results from executing(act 330) the authentication process. For example, the act or acts 335of determining may be performed entirely by the wireless powertransmitter 1. If the second mode is not allowed (e.g., theauthentication process did not complete successfully), then the wirelesspower receiver 11 may be limited to operating (act 340) in the firstmode for the remainder of the wireless power-transfer session.

If the authentication process completes successfully, the wireless powerreceiver 11 can store (act 345) session attributes. The sessionattributes can be those described above in connection with act 245.According to some embodiments, the wireless power receiver 11 can storethe session attributes locally (e.g., in non-volatile memory), and/orsend them to the wireless power transmitter 1 to be stored by thetransmitter. According to some embodiments, sending the sessionattributes to the wireless power transmitter may automatically grant thetransmitter permission to proceed with foreign object detection andpower transfer at a higher power level.

The wireless power receiver 11 can further interrupt (act 350) wirelesspower reception from the receive coil 12. In some cases, theinterruption of wireless power transfer may be in response to a commandissued by the transmitter 1. To interrupt wireless power reception, thereceiver may disable power flow from the receive coil 12 as describedabove. The interruption of wireless power reception can allow thewireless power transmitter 1 to execute (act 255) foreign objectdetection (e.g., by evaluating the Q factor).

According to some embodiments, the wireless power receiver 11 canfurther participate in establishing (act 360) a power contract with thewireless power transmitter 1 for the first mode of operation, and thenreceive (act 365) session attribute information. Session attributeinformation can be received from the wireless power transmitter 1 insome cases, if stored there during the interruption (act 350) ofwireless power reception. In some implementations, session attributeinformation can be retrieved from local memory (e.g., non-volatile orvolatile memory) that is in communication with the receiver 11 or itscontrol logic 16. In some cases, receiving (act 365) session attributeinformation can include validating the session attribute information bythe receiver 11. For example, the receiver may compare received sessionattribute information against session attribute information that itstored in its memory 17, at the time that the session attributeinformation was prepared and sent to the transmitter, to verify that atleast some of the information matches.

In some embodiments, the receiving (act 365) of the session attributeinformation can effectively restore authentication status at thewireless power receiver 11, without the transmitter and receiverundergoing the authentication process again. This can allow the wirelesspower receiver 11 and transmitter 1 to proceed quickly to acts ofestablishing (acts 370, 270) a power contract in the second mode ofoperation, performing calibration (acts 375, 275), and operating (acts380, 280) in the second mode. When establishing (act 370) power contractin the second mode of operation, the wireless power receiver 11 maytransmit at least some of the session attribute information stored withthe session attributes to the wireless power transmitter 1.

In embodiments of wireless power transfer methods 200, 300, actsassociated with retrieval and use of session attributes can be thoughtof as an abbreviated authentication process or re-authentication processthat is performed after interruption (act 350) of wireless powerreception by the wireless power receiver 11. In some cases, there-authentication can be checked by only one device. For example, onlythe wireless power transmitter 1 may check for valid session attributeinformation provided by the wireless power receiver 11 whentransitioning to the second mode of operation (e.g., while establishing(act 370) a power contract in the second mode of operation). In otherembodiments, both the wireless power receiver 11 and transmitter 1 maycheck session attribute information when transitioning to the secondmode of operation. For example, the wireless power receiver 11 may checkretrieved session attribute information (from act 365) to determine thatthe session is being maintained with the same wireless power transmitter1.

The methods 200, 300 described above pertain to two modes of operation,a low-power mode (e.g., a basic performance mode) and a high-power mode(e.g., an extended performance mode). The methods can apply to moremodes of operation (e.g., additional high-power modes of operation). Insome cases, the two modes of operation may pertain to transitions up ordown in power level. For example, whenever an increase or decrease inpower level is requested by a wireless power receiver 11, storage and/orexchange of session attributes, interruption of wireless power transfer,foreign object detection, and re-establishment of wireless powertransfer can occur. As such, the first mode and second mode in theillustrated methods 200, 300 may pertain to high-power and low-powermodes, respectively.

As may be further appreciated, the methods 200, 300 can pertain totransitions from non-privileged modes of operation (analogous to thelow-power mode) and privileged modes of operation (analogous to thehigh-power mode). A non-privileged mode may be a basic power transfermode that is widely available to wireless power receivers and wirelesspower transmitters. For example, neither the wireless power receiver andwireless power transmitter need be certified or authorized to access thenon-privileged mode of operation. A privileged mode of operation may bea mode that contains higher performance features (e.g., energy savingfeatures, higher power transfer, device diagnostic features, etc.). Aprivileged mode need not involve power transfer at a higher power levelthan a non-privileged mode. As such, the first mode and second mode inthe illustrated methods 200, 300 may pertain to non-privileged andprivileged modes, respectively.

As an example, a method of receiving power wirelessly by a wirelesspower receiver during a wireless power transfer session may include actsof: establishing wireless power reception from a wireless powertransmitter in a non-privileged mode of operation; executing anauthentication process with the wireless power transmitter; sendingsession attribute information to memory, wherein the session attributeinformation includes at least some information relating to theauthentication process; receiving session attribute information afterinterruption of wireless power reception in the non-privileged mode ofoperation at the wireless power receiver; and establishing wirelesspower reception from the wireless power transmitter in a privileged modeof operation after receiving the session attribute information. Circuitcontrol logic may be configured to operate in this manner.

As another example, a method of transmitting power wirelessly by awireless power transmitter may comprise acts of: establishing wirelesspower transmission to a wireless power receiver in a non-privileged modeof operation; executing an authentication process with the wirelesspower receiver; performing a foreign object detection process during atime when wireless power reception at the wireless power receiver at thefirst power level is interrupted after executing the authenticationprocess; re-establishing wireless power transmission to the wirelesspower receiver in the non-privileged mode of operation; and establishingwireless power transmission to the wireless power receiver in aprivileged mode of operation after performing the foreign objectdetection process. Circuit control logic may be configured to operate inthis manner.

The methods 200, 300 of wireless power transfer described above inconnection with FIG. 2A through FIG. 3 include various functionalitiesthat can be implemented with logic circuitry or processor(s) and code.Code written to perform such functionalities can be stored onnon-transitory computer-readable media, so that it can be loaded on toone or more processors (or used to configure logic circuitry) to adaptthe one or more processors (or logic circuits) and related circuitry toperform the functionalities.

Accordingly, a wireless power transmitter 1 may be controlled usingcontroller 5 and a wireless power receiver 11 may be controlled usingcontrol logic 16, which may be implemented by suitable logic circuitry.For example, the controller 5 or control logic 16 may be implementedusing hardware or some combination of hardware, firmware, and code(software). When implemented using code, suitable code can be executedon a suitable processor (e.g., a microprocessor) or collection ofprocessors. The one or more processors can be implemented in numerousways, such as with dedicated hardware, or with general purpose hardware(e.g., one or more processors) that is programmed using code to performthe functions described above.

In this respect, it should be appreciated that one implementation of atleast a portion of the embodiments described herein comprises at leastone computer-readable storage medium (e.g., RAM, ROM, EEPROM, flashmemory or other memory technology, or other tangible, non-transitorycomputer-readable storage medium) encoded with computer code (i.e., aplurality of executable instructions) that, when executed on one or moreprocessors, performs at least some of the above-discussedfunctionalities of one or more embodiments. In addition, it should beappreciated that the reference to code which, when executed, performsany of the above-discussed functionalities, is not limited to anapplication program running on a host computer. Rather, the terms codeand software are used herein in a generic sense to reference any type ofcomputer code (e.g., application software, firmware, microcode, or anyother form of computer instruction) that can be employed to program oneor more processors and/or logic circuitry to implement functionalitiesdescribed herein.

Various aspects of the apparatus and techniques described herein may beused alone, in combination, or in a variety of arrangements notspecifically discussed in the embodiments described in the foregoingdescription and is therefore not limited in its application to thedetails and arrangement of components set forth in the foregoingdescription or illustrated in the drawings. For example, aspectsdescribed in one embodiment may be combined with aspects described inother embodiments.

Use of ordinal terms such as “first,” “second,” “third,” etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” “having,” “containing,” “involving,” andvariations thereof is meant to encompass the items listed thereafter andequivalents thereof as well as additional items.

What is claimed is:
 1. A controller for a wireless power transmitterthat is adapted with code to: establish wireless power transmission to awireless power receiver at a first power level; execute anauthentication process with the wireless power receiver; send sessionattribute information relating to the authentication process to memory;perform a foreign object detection process during a time when wirelesspower reception at the first power level at the wireless power receiveris interrupted; and transmit at least some of the session attributeinformation retrieved from the memory to the wireless power receiverprior to transmitting power wirelessly at a second power level that ishigher than the first power level.
 2. The controller of claim 1, whereinthe controller is further adapted with code to: establish for a secondtime wireless power transmission to the wireless power receiver at thefirst power level after executing the authentication process; andestablish wireless power transmission to the wireless power receiver atthe second power level after establishing for the second time wirelesspower transmission to the wireless power receiver at the first powerlevel.
 3. The controller of claim 2, wherein the controller is furtheradapted with code to subsequently perform a calibration process forwireless power transfer with a foreign object present in a wirelesspower transfer region during wireless power transfer at the second powerlevel.
 4. The controller of claim 1, wherein the controller is furtheradapted with code to receive at least a portion of the session attributeinformation from the wireless power receiver.
 5. The controller of claim1, further comprising sending a command to the wireless power receiverthat causes the wireless power receiver to interrupt wireless powerreception after executing the authentication process.
 6. The controllerof claim 1, wherein the controller is further adapted with code toevaluate a Q factor of a transmit coil of the wireless powertransmitter.
 7. A method of transmitting power wirelessly by a wirelesspower transmitter, the method comprising: establishing wireless powertransmission to a wireless power receiver in a first mode of operation;executing an authentication process with the wireless power receiver;performing a foreign object detection process during a time whenwireless power reception at the wireless power receiver in the firstmode of operation is interrupted after executing the authenticationprocess; re-establishing wireless power transmission to the wirelesspower receiver in the first mode of operation; and establishing wirelesspower transmission to the wireless power receiver in a second mode ofoperation after performing the foreign object detection process.
 8. Themethod of claim 7, further comprising: sending session attributeinformation relating to the authentication process to memory beforeperforming the foreign object detection process; and transmitting thesession attribute information retrieved from the memory to the wirelesspower receiver after performing the foreign object detection process andprior to establishing wireless power transmission to the wireless powerreceiver in the second mode of operation.
 9. The method of claim 8,further comprising receiving at least a portion of the session attributeinformation from the wireless power receiver.
 10. The method of claim 7,further comprising sending a command to the wireless power receiver thatcauses the wireless power receiver to interrupt wireless power receptionafter executing the authentication process.
 11. The method of claim 7,further comprising establishing for a second time wireless powertransmission to the wireless power receiver in the first mode ofoperation after executing the authentication process.
 12. The method ofclaim 11, further comprising establishing wireless power transmission tothe wireless power receiver in the second mode of operation afterestablishing for the second time wireless power transmission to thewireless power receiver in the first mode of operation, wherein thesession attribute information transmitted to the wireless power receiverpermits the establishing of wireless power transmission to the wirelesspower receiver in the second mode of operation.
 13. The method of claim11, further comprising subsequently performing a calibration process forwireless power transfer with a foreign object present in a wirelesspower transfer region during wireless power transfer in the second modeof operation.
 14. The method of claim 7, wherein the foreign objectdetection process comprises evaluating a Q factor of a transmit coil ofthe wireless power transmitter.